The present invention relates as indicated to a drying tower for elongated tubes in general and to an air manifold system associated with said tower for sequentially forcing heated air at controlled velocities through the elongated tubes in opposite directions to dry the coated interior diameter of such tubes in particular.
Continuous tube forming and galvanizing process lines are well known in the art as shown, for example, by U.S. Pat. Nos. 3,122,114 and 3,845,540. Such process lines operate at speeds from 50 to 400 feet per minute rapidly to produce the galvanized tube or pipe product. Such galvanized tube may be interiorly and exteriorly coated either on the line as shown in U.S. Pat. Nos. 3,559,280; 3,616,983 and 3,768,145 or off the line after cut-off.
When the inner diameter of the galvanized tube has been painted, the cut lengths of such tube must be properly interiorly dried to provide a uniform paint surface. One method of heating interiorly painted tubes has been proposed and pursued for drying the inner diameter of such tube.
Specifically, the interiorly painted tubes may be conveyed through a large gas fired furnace. However, the use of such gas fired furnace has several drawbacks. Specifically, the size of the costly furnace requires significant floor area in the plant, and the operation of such furnace is rather expensive. Moreover, the whole tube is being heated in such a furnace, requiring the tubes to be in the furnace for extended periods of time and to be conveyed at relatively slow feed rates in order to bring the tube to the necessary temperature to attain the interior effect necessary. Therefore, the feed rate through the furnace is considerable slower than the operating speeds of a continuous galvanizing process line resulting in decreased efficiency in using such line and in reduced production.
It is accordingly the principle object of the present invention to provide a drying tower for interiorly coated tube. By providing a tower apparatus having a conveyor with vertical ascent and descent paths for the interiorly painted tubes, the drying can be effected by apparatus occupying minimal floor space and operating at relatively high speeds generally compatible with a continuous galvanizing line.
It is yet another object of the present invention to force heated air at controlled velocities through the interiorly painted tubes in one direction during ascent and to force heated air at increased controlled velocities through the tubes in the opposite direction during descent. The use of bi-directional air flow reduces the possibility of an air pocket being formed during drying and thereby improves the uniformity of the drying operation. The use of lower velocity heated air in one direction during ascent permits the paint adequately to set before the higher velocity air for final drying is directed therethrough in the opposite direction on descent.
It is still another object of the present invention to provide a drying tower that may be readily adjusted to handle interiorly painted tubes of varying length. To this end, one of the end tower frames carrying air manifold system ducting is selectively movable relative to the other tower frames so that tubes of varying lengths may be selectively conveyed and dried with the air nozzles for such ducting always being positioned at a predetermined spacing from the ends of the tube aligned therewith.
Other objects and advantages of the present invention will become apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.